1. Field of the Invention
This invention relates to building materials, and more particularly, to a building material comprising a fiber cement substrate, a polymer film and a plurality of resin impregnated sheets that is both pre-finished and durable.
2. Description of the Related Art
Fiber cement in recent years has become popular for use as a building material instead of more conventional materials such as wood, metal and plastics. Fiber cement has better water resistance than wood and is more resistant to rotting, cracking or splitting than wood. Also, fiber cement does not rust like metal, and is more durable to weathering than plastics. For instance, fiber cement products such as James Hardie Building Products"" HARDIPLANK(copyright) install just as easily as wood siding, but offer a lifetime of low maintenance. Fiber cement siding is a durable, attractive alternative to traditional wood composite, cedar, vinyl, brick or stucco sidings.
Despite these advantages, fiber cement may not always have the desired exterior look and feel for a particular application. Moreover, conventional fiber cement materials are often painted or subject to other types of post-production or on-site finishing to give the material its desired appearance and exterior protection. However, exposure of paint to natural weathering and other factors can lead to chalking of the surface and loss of polymer in the paint film. Paint surfaces are also very thin, generally on the order of one to two mils, and because of that are subject to chipping, peeling and scratching from surface abuse.
Laminates comprised of a core having a sheet laminate comprised of a plurality of resin impregnated paper sheets adhered to the core are known in the art. Known core materials include engineered wood panels such as MDF (medium density fiber board) and particle boards. These products may perform satisfactorily in dry areas, but in areas subject to moisture these products have a tendency to swell, which misaligns the edges of the structure.
U.S. Pat. No. 5,425,986 discloses a laminate structure comprising a core of fiber cementboard laminated to resin impregnated sheets. The differential dimensional movement of the core and the laminate through various environmental conditions can lead to induced stresses between the fiber cement and resin impregnated sheets which often leads to splitting of the core or delamination. This is exaggerated by environments which experience high moisture followed by periods of dryness or heat and low humidity.
Accordingly, what is needed is a building material incorporating the durability and moisture resistance of fiber cement while also having a desired exterior look and feel. In addition, what is needed is a building material having an exterior surface that is pre-finished and durable to scratch and wear, while also maintaining strong adhesion to the fiber cement, and does not split, crack or delaminate when exposed to severe environmental conditions or wet/dry cycling.
One embodiment of the present invention relates to a building material comprising a fiber cement substrate having a first side and a second side, at least one resin impregnated paper over at least one of the first and second sides, and a stress-relieving polymeric film between the fiber cement substrate and the at least one resin impregnated paper, the polymer film acting as a stress relaxer between the fiber cement substrate and the at least one resin impregnated paper.
In another embodiment, a film for joining fiber cement to a resin penetrated paper is provided. This film comprises a polymer adapted to balance stresses between the fiber cement and the resin penetrated paper.
In another embodiment, a method is provided for bonding a fiber cement substrate having a surface to at least one resin impregnated paper to form a building material. The method comprises coating at least a portion of the surface of the fiber cement substrate with a stress-relieving polymer film, the polymer film being capable of preventing delamination between the substrate and the at least one resin impregnated paper. The at least one resin impregnated paper is pressed against the polymer film and the substrate.